Known transformers can be used in electrical energy distribution systems in order to couple power supply units with different voltage levels to one another. Transformers can be designed as dry-type transformers with a voltage level close to a consumer or generator and can have nominal voltages, for example, in the range from, for example, 1 kV to 6 kV on the low-voltage side and nominal voltages in the range from, for example, 10 kV to 30 kV on the high-voltage side, wherein corresponding nominal powers lie in the range from, for example, 0.5 MVA to 10 MVA. However, transformers such as this can be used in the field of wind power installations, where the nominal power of a transformer is directed towards the power of an associated wind power installation.
Due to the high nominal currents in the low-voltage range, which can be, for example, some 100 A, the low-voltage windings can be designed in a manner wound from a ribbon conductor, wherein the width of a ribbon conductor corresponds to at least the complete axial length of a respective transformer winding. Depending on the embodiment and specifications on the transformer, the number of low voltage-side turns can be, for example, in the region of ten turns, for example, in applications for wind power installations, where the voltage generated on the generator side can be correspondingly low and can be set to a higher operating level by the transformer.
For the purposes of regulation, a known procedure can be to provide the high voltage-side winding(s) of a transformer with a plurality of taps, which can be selected by a respective on-load tap changer, for example, with the result that the transformation ratio of the transformer can thus be changed within a regulation range. Increased regulability can be needed in applications for wind power installations in order to help ensure the transformer is adapted to the boundary conditions resulting from different wind conditions.
The active part of a transformer can have a closed iron circuit and at least one high-voltage and low-voltage winding with an integer number of closed turns around the respective core limb. The induced voltage per closed conductor loop can be dependent on the mains frequency, flux density and core cross section.
An on-load tap changer arranged on the high-voltage side can be complex to make due to the high voltage demand and that regulation of the voltage can take place minimally in that voltage graduation, which can correspond to the induced voltage of a complete turn. In the case of voltage regulation, the minimum regulation stage can be limited to the voltage difference between two turns. For example, in the case of the low voltage-side ribbon windings disclosed above because, owing to the relatively low total number of turns, for example, in the region of ten, fine regulation around the nominal transformation may not be possible.
In accordance with an exemplary embodiment, the disclosure can provide a transformer which can enable the voltage on the low-voltage side to be regulated in smaller voltage steps, and wherein a corresponding on-load tap changer can be made simpler due to the then lower voltage demand.